ballast water exchange
(D)The term “ballast water exchange” means the replacement of water in a ballast water tank using 1 of the following methods: (i)Flow-through exchange, in which ballast water is flushed out by pumping in midocean water at the bottom of the tank if practicable, and continuously overflowing the tank from the top, until 3 full volumes of water have been changed to minimize the number of original organisms remaining in the tank. (ii)Empty and refill exchange, in which ballast water taken on in ports, estuarine waters, or territorial waters is pumped out until the pump loses suction, after which the ballast tank is refilled with midocean water.